The 3GPP (Third Generation Partnership Project)-standard relates to technology based on radio access networks, such as the UTRAN, which is a radio access network architecture providing W-CDMA (Wideband Coding Division Multiple Access) to mobile terminals. Telecommunication systems according to the 3GPP-standard offer high and variable bit-rates and are capable of providing new types of services to the users, involving real-time audio and video, still images and text, e.g. news, sport results and weather forecasts. By means of the High Speed Downlink Packet Access (HSDPA)-feature of the 3GPP-standard, the system capacity and the peak data rates is increased in the downlink direction, and the transfer delays are reduced.
In a telecommunication system according to the 3GPP-standard, a mobile terminal, such as e.g. a cellular telephone provided with a SIM (Subscriber Identity Module)-card, is commonly referred to as a UE (User Equipment), and communicates with a core network connected to external networks, e.g. the Internet and the PSTN (the Public Switched Telephone Network), via a UTRAN covering a geographical area divided into cells with unique identities. Each cell is served by a base station device, which in the 3GPP is referred to as a Node B, and the radio coverage of a cell is provided by a base transceiver station (BTS) at the serving base station (i.e. Node B) site over an air-interface. One Node B normally serves more than one cell, and the Node Bs are controlled by a radio resource server, which is managing the transmission resources of the UTRAN and is connected to one or more core networks. The radio resource server is commonly referred to as an RNC (Radio Network Controller) in the present 3GPP-standard, and comprises a cell controlling entity, which owns the cell resource and handles the signalling toward the Node B, and a UE controlling entity for handling the signalling toward the UE. Conventionally, the cell controlling entity is referred to as a Controlling RNC, C-RNC, and the UE controlling entity is referred to as a Serving RNC, S-RNC.
FIG. 1 illustrates an exemplary, conventional radio access network architecture, providing W-CDMA to UEs, of which only one UE is shown in this figure. The UE 1 is located in a cell, 2, which is served by Node B, 3, and the Node B and the UE communicates over an air-interface, i.e. a Uu-interface. The Node B is controlled by a cell controlling entity 4, i.e. a C-RNC, and the individual UE is controlled by a UE controlling entity, 5, i.e. a S-RNC, the cell controlling entity and the UE controlling entity forming a radio resource server, 6, i.e. radio network controller, RNC.
A cell controlling entity 4 of a radio resource server 6, e.g. a C-RNC, controls the signalling towards several Node Bs, and the Node B forwards the signals over an air interface to the UEs located in the cells served by the Node B. A UE controlling entity 5 of a radio resource server, e.g. an S-RNC, controls the signalling towards individual UEs by means of stored context information, and normally remains S-RNC while a UE is connected to the RAN, also when the UE moves over a large geographical area and passes through several cells, until the UE is disconnected. Alternatively, a change of S-RNC is performed with a S-RNC relocation procedure. Due to cell the relocation of a UE, the cell controlling entity may not be located in the same radio resource server as the UE controlling entity. Alternatively, the cell controlling entity may be physically located in connection with base station device.
Regarding the radio resource control (RRC), the UE operates either in an Idle Mode or in a Connected Mode, and the UE automatically enters the Idle Mode at power on, before a connection is established between the UE and a UTRAN. When a connection is established, the UE enters a Connected Mode, and is assigned a U-RNTI (a UTRAN Radio Network Temporary Identity), which can be used in any cell of UTRAN. Within the Connected Mode, there are four different states, i.e. the CELL_DCH (Dedicated Channel) state, the CELL_FACH (Forward Access Channel) state, the CELL_PCH (Paging Channel) state and the URA_PCH state. However, to be capable of HDSPA reception, a UE must be in the connected CELL_DCH state, in which a dedicated physical channel is allocated to the UE for the uplink and downlink, while a combination of dedicated and shared transport channels are available to the UE.
In W-CDMA, the information data is CDMA coded before the transmission, and the same frequency can be used simultaneously by all UEs. The CDMA coding involves a first step of spreading (channelization) for establishing a fixed predefined bit-rate, by replacing each information data bit by a spreading code (channelization code). The spreading factor (SF) indicates the length of the code, being between 4 and 256 bits in uplink and between 4 and 512 bits in downlink. A second step of the CDMA coding involves scrambling, in which the spread information data is coded with a unique scrambling code.
In order to support the HSDPA, the W-CDMA is extended by a new downlink transport channel, the HS-DSCH (High Speed Downlink Shared Channel), and the HS-DSCH is mapped onto one or several HS-PDSCH (High Speed Physical Downlink Shared Channels), received simultaneously by the UE. Thereby, the HS-DSCH provides an enhanced support in the downlink direction for UEs in the connected CELL_DCH state, facilitating interactive, background, and streaming radio access bearer services, and allows a higher-order modulation and a faster link adaptation than earlier transport channels. Furthermore, the Node B is provided with a new MAC sub-layer, MAC-hs (Medium Access Control High Speed, for the HS-DSCH transmission, and the MAC-hs supports fast hybrid ARQ (Automatic Repeat Request) with soft combining, increasing the system capacity as well as substantially reducing the delays. The HS-DSCH transmission uses a common spreading (channelization) code resource, with is shared dynamically by several UEs in the time domain and code domain, but primarily in the time domain. The shared code resource consists of up to 15 channelization codes having a fixed spreading factor, SF 16. Dynamic allocation of channelization codes from the shared code resource is performed with an interval of 2 ms, which also corresponds to the duration of the HS-DSCH Transmission Time Interval (TTI).
A DPCH (Dedicated Physical Channel) transmits data between a Node B and a UE served by the Node B, and the DL-DPCH (Down Link Dedicated Physical Channel) provides a down-link for transmitting signals or data from the Node B to UE, while the UP-DPCH (Up Link Dedicated Physical Channel) provides the up-link for transmitting the signals or data from the UE to the Node B. The physical channels transfer data during frames, corresponding to predefined time intervals. An SFN (System Frame Number) can be used in synchronization procedures, and the SFN is broadcast on a P-CCPCH (Primary Common Control Physical Channel). The SFN has a duration of 10 ms, a range of 0-4095, and increments with each received frame. A CFN (Connection Frame Number) can also be used in a synchronization procedure with respect to a particular UE, and the CFN and is related to the SFN. The CFN has a range of 0-255, incremented with each received frame.
In the downlink, the HS-DSCH employs separate physical Shared Control Channels (HS-SCCH) to convey the fast signalling information required for support of the link adaptation, hybrid ARQ (Automatic Repeat Request) and resource allocating functions. The HS-SCCH uses a fixed spreading factor, SF 128, and has a time structure based on a sub-frame having a length of 2 ms. The timing of the HS-SCCH is synchronized with the P-CCPCH, on which the SFN of the cell is transmitted, which means that every 10 ms the start of the HS-SCCH sub-frame is aligned with the start of the P-CCPCH frame. Regarding the HS-PDSCH sub-frame, the HS-SCCH sub-frame starts two time slots prior to the start of the HS-PDSCH sub-frame.
In the uplink, the HS-DSCH introduces a separate physical channel, the Dedicated Physical Control Channel (HS-DPCCH), for providing feedback hybrid ARQ information as well as channel quality information (CQI), and the HS-DPCCH is code multiplexed with the DSCH. Similarly to the HS-PDSCH and HS-SCCH, the HS-DPCCH uses a 2 ms sub-frame structure, with a timing defined in relation to the HS-PDSCH, such that the feedback hybrid ARQ information regarding an HS-PDSCH sub-frame is sent approximately 19200 chips (rounded to the closest 256 chip boundary of the UL-DPCH) after the end of the HS-PDSCH sub-frame.
The transport channels, the physical channels and the radio bearers are configured and reconfigured by means of reconfiguration procedures defined in the 3GPP standard, in which the UTRAN, i.e. the Node B, performs up-link synchronization procedures, and the UE performs down-link synchronization procedure.
Conventionally, a reconfiguration procedure is initiated by a cell controlling entity of the radio resource server, i.e. the C-RNC, sending a reconfiguration requesting message to the Node B. The Node B sends a radio link updating message to the UE controlling entity of a radio resource server, i.e. the S-RNC, which sends an RRC reconfiguration message to a UE and a RNSAP/NBAP reconfiguration message to the Node B handling the UE, the RNSAP/NBAP/RRC reconfiguration message comprising configuration parameters, as well as an indication of the activation time of the reconfiguration, by including an activation time IE. The start of the synchronization procedures is controlled by the activation time IE, pointing to a specific CFN.
However, the existing solution according to prior art involves a number of drawbacks. For example, according to a present 3GPP standard UTRAN Iub interface NBAP (Node B Application Part) signalling protocol, the C-RNC sends a PHYSICAL SHARED CHANNEL RECONFIGURATION REQUEST-message as a reconfiguration request to a Node B, to be used to configure or reconfigure HS-DSCH related resources in a cell. The HS-DSCH (High Speed Downlink Shared Channel) is a new HSDPA-related downlink transport channel, and the parameters that can be set by this message, in an FDD (Frequency Division Duplex)-mode, include the following:                HS-PDSCH and HS-SCCH Total Power, which sets the maximum transmission power allowed to be used for HS-PDSCH and HS-SCCH transmission,        HS-PDSCH and HS-SCCH Scrambling Code,        HS-PDSCH FDD Code Information, indicates the channelization codes reserved for HS-PDSCH transmission,        HS-SCCH FDD Code Information, indicates the channelization codes allocated for HS-SCCH transmission.        
In order to allow a synchronized change of the configurations used in the downlink, said PHYSICAL SHARED CHANNEL RECONFIGURATION REQUEST-message, issued by the C-RNC, is further provided with an SFN IE (System Frame Number Information Element), enabling the Node B to activate the new configuration at the head boundary of that specified SFN. The synchronized reconfiguration at a given SFN will minimize the data loss and throughput degradation caused by a mismatch in the channelization or scrambling codes between UTRAN and a UE. Upon receipt of a PHYSICAL SHARED CHANNEL RECONFIGURATION REQUEST-message, according to a present 3GPP-standard, from the C-RNC, including the SFN IE, the Node B performs a reconfiguration of the downlink parameters by switching to the new configuration at the indicated SFN. In case this reconfiguration has an effect on the downlink configuration set up towards the UE regarding the HS-DSCH (High Speed Downlink Shared Channel), the Node B shall notify the S-RNC of the change of the downlink parameters by issuing a RADIO LINK PARAMETER UPDATE INDICATION-message towards the C-RNC, to be further relayed to the S-RNC, in case the C-RNC and the S-RNC are located in different nodes. In case the C-RNC and the S-RNC are located in the same node, this message will be forwarded as a node internal message. Upon receipt of this RADIO LINK PARAMETER UPDATE INDICATION-message, the S-RNC initiates reconfiguration procedures towards the Node B and the UE, in order to change the downlink and uplink HS-DSCH configuration applicable to the UE.
The reconfiguration procedure performed from the S-RNC towards the Node B uses a NBAP/RNSAP RADIO LINK RECONFIGURATION-message, which according to present 3GPP-standard 3GPP TS 25.423 and 25.433 may comprise the following:
RADIO LINK RECONFIGURATION PREPARE
RADIO LINK RECONFIGURATION READY
RADIO LINK RECONFIGURATION COMMIT
RADIO LINK RECONFIGURATION FAILURE
RADIO LINK RECONFIGURATION CANCEL
RADIO LINK RECONFIGURATION REQUEST
RADIO LINK RECONFIGURATION RESPONS
The above-described NBAP/RNSAP RADIO LINK RECONFIGURATION-message performs for instance:                Configuration of CQI on the HS-DPCCH        Configuration of power offsets for different information on the HS-DPCCH        
The reconfiguration procedure performed from S-RNC towards the UE is performed with RRC RB reconfiguration messages, which according to present 3GPP-standard 3GPP TS 25.331 may comprise the following:
RADIO BEARER SETUP
RADIO BEARER RECONFIGURATION
RADIO BEARER RELEASE
TRANSPORT CHANNEL RECONFIGURATION
PHYSICAL CHANNEL RECONFIGURATION
However, since the reconfiguration of the Node B, ordered by the C-RNC, is not perfectly synchronized with the reconfiguration of UE, ordered by the S-RNC, the HSDPA performance may degrade due to the resulting configuration mismatch between the UTRAN and the UE. The problem with achieving a synchronized reconfiguration of downlink HSDPA-related parameters is caused by the difficulty to set up a new HS-DSCH configuration at a specific SFN regarding a UE in the CELL_DCH state. This is due to the RADIO LINK PARAMETER UPDATE INDICATION-message, issued by the Node B, not including any information element informing the S-RNC of the exact point in time when the new downlink configuration shall be taken into use, i.e. switching time, since the conventional Dedicated NBAP/RNSAP/RRC reconfiguration messages, related to a specific UE, only allows reconfigurations at a given CFN (Connection Frame Number), and not at a given SFN. Furthermore, a UE in the CELL_DCH state does not keep track of the SFN value, only of the P-CCPCH timing.
Therefore, the aim of the present invention is to solve the problems described above in order to provide synchronized HSDPA-related reconfigurations between the UTRAN and a UE.